Researchers have developed a new antibody approach that may help fight a broad range of cancers, including colon cancer, according to a new study. The antibody targets the SIRPα protein, which is thought to help cancer cells evade surveillance by the immune system and survive.
The study was published in the journal JCI Insight, titled “Anti-SIRPα Antibodies As A Potential New Tool For Cancer Immunotherapy.”
Macrophages are immune cells that engulf and destroy cancer cells, but previous studies led by Prof. Takashi Matozaki from Kobe University in Japan revealed that when the SIRPα protein, present on the surface of macrophages, bind to the CD47 protein, located on the outer layer of cancer cells, macrophages can no longer eliminate them.
Now, Matozaki and his team found that cells isolated from mouse and human kidney cancer and melanoma expressed high levels of SIRPα, helping these cells escape from macrophages. Researchers found that treatment with an anti-SIRPα antibody in mice with kidney cancer or melanoma blocked the interaction with CD47, inhibiting tumor growth and metastasis.
Similar effects were observed in mice injected with cells derived from human B-cell lymphoma.
Further analyses revealed that the antibody works in two ways: It induces the activation of macrophages by directly binding to SIRPα, and blocks the immunosuppressive CD47-SIRPα interaction.
Importantly, the study also showed that the anti-SIRPα antibody improves the effect of antibodies targeting the CD20 and PD-1 proteins to prevent cancer survival.
Results showed that in mice with colon cancer, a combined treatment of anti-SIRPα antibodies and anti-CD20 (rituximab) or anti-PD-1 antibodies had a stronger effect on blocking cancer growth than when these drugs were administered alone.
Although the complete mechanism of action of these antibodies remain elusive, researchers believe their results support the potential use of anti-SIRPα antibodies for the treatment of a broad range of cancer types.
“Together, these findings suggest that targeting both the CD47/SIRPα and PD-1/PD-L1 axes provides a new approach to immunotherapy for a broad range of cancers,” the researchers wrote.
However, they cautioned that more studies are needed to understand how the anti-SIRPα antibody causes these anti-tumor effects.